Abstract A bounding surface model in general stress space is formulated for soft rock subjected to drained and undrained condition. Specifically, a UYC bounding surface is defined based on unified yield criterion by introducing bounding surface plasticity, and it can degenerate to a bounding surface adopting Mohr-Coulomb criterion or Twin-shear criterion; a UYC loading surface that is similar to the UYC bounding surface is defined; a mapping rule in general stress space is given to consider the plastic strain inside the UYC bounding surface; a modified hardening parameter and a modified stress-dilatancy is proposed to capture the residual strength and volumetric strain of soft rock, respectively. The comparison between model prediction and experimental results shows that the constitutive model well predicts the mechanical behaviours of soft rocks subjected to drained and undrained compression condition. Besides, the proposed model overcomes the limitation that the plastic strain of soft rock can’t be well captured by the traditional constitutive models based on unified strength theory.

中文翻译：

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排水和不排水条件下软岩的增强边界面塑性模型

摘要 针对排水和不排水条件下的软岩，建立了一般应力空间中的边界面模型。具体而言，通过引入边界面塑性，基于统一屈服准则定义UYC边界面，并退化为采用Mohr-Coulomb准则或Twin-shear准则的边界面；定义了一个类似于 UYC 边界面的 UYC 加载面；给出一般应力空间的映射规则，考虑UYC边界面内的塑性应变；提出了修正的硬化参数和修正的应力膨胀系数，分别用于捕捉软岩的残余强度和体积应变。模型预测与实验结果对比表明，本构模型较好地预测了排水和不排水压缩条件下软岩的力学行为。此外，该模型克服了传统基于统一强度理论的本构模型不能很好地捕捉软岩塑性应变的局限性。